1. Field of the Invention
This invention relates generally to systems for removing gas bubbles from liquids, and more particularly to systems for removing gas or air bubbles from liquids intended for introduction into the bloodstream of a patient.
2. Description of the Prior Art
In medicine, the elimination of gas bubbles from a liquid to be injected into a patient's bloodstream is of great clinical importance. Many patients annually receive fluids from intravenous (IV) infusion devices connected through a catheter to a blood vessel. Additionally, medical practitioners are making greater use of arterial sensing devices which are introduced directly into the bloodstream, which devices can also introduce gas bubbles.
A bubble of gas, usually air, that may be trapped in the liquid is potentially dangerous to the patient. This air bubble can cause a gas or air embolism, which can obstruct blood circulation and perhaps cause an infarction, thereby cutting off blood circulation. As little as 0.1 ml of gas in an arterial line can be dangerous--even fatal--to an adult human.
One method for dealing with this problem is for standard IV infusion bottles to be held in a vertical position, for bubbles to rise to the top; this is common practice.
Additionally, hydrophilic filters are used in-line in intravenous infusion devices, between the IV supply source and the patent. A hydrophilic filter permits passage of the liquid but prevents the passage of gas bubbles into the IV feed line. The hydrophilic filter is housed in a conventional "dripmeter", such as the "Millipore.RTM.IVEX-H.P. Filterset", No. 4524, manufactured by Abbott Laboratories of North Chicago, Ill.
However, a gas or air bubble of sufficient size will block the passage of liquid into the patient, necessitating the discarding of the commonly used drip device connected to the feed line and the starting of the infusion anew. Also, it is difficult to visually detect when liquid flow has stopped due to blockage, because the dripmeter will look the same when it is either completely full of air or liquid, both of which are typically clear.
Other apparatus such as arterial sensing devices are currently purged of air bubbles after drawing blood, and must be monitored by careful visual inspection. No device assures that gas or air bubbles have been forced out of the patient liquid supply line.